Analyzing chemical composition of samples is important in many contexts, including identifying and segregating metal types (particularly various types of iron and steel) in outdoor metal recycling facilities, quality control testing in factories and forensic work. Several analytical methods are available.
Optical emission spectroscopy (OES) is a mature, robust technology for the elemental analysis of materials. In OES, a small quantity of sample material is vaporized and excited above atomic ground state. Emissions characteristic of elements in the vaporized sample are captured by a light guide, which sends the light to an analyzing unit, including a spectrometer, which produces and interprets a spectrum of light, so as to yield the elemental composition of the sample.
For metal samples, the prevalent techniques for generating emission spectra use either an electric arc or a spark, or both, to vaporize a small quantity of the sample to be analyzed. Alternatively, laser-induced breakdown spectroscopy (LIBS) or glow discharge (GD) may be used to vaporize and excite an emission sample. A survey of OES analytical techniques may be found in Slickers, Automatic Atomic-Emission Spectroscopy, Second Edition (1993), which is incorporated herein by reference.
One of the problems of available hand-held OES analyzers remains the small amount of light provided to the input of the built-in spectrometers, which inevitably limits signal-to-noise ratio and, therefore, the precision of spectral analysis of subject materials.